Gas-insulated switching device

ABSTRACT

An interruption and disconnecting device for high or medium voltage applications including a disconnection chamber and an interruption pole having a casing that delimits a free volume accommodating an interruption chamber. The interruption chamber contains a moving contact and a fixed contact. The interruption pole and the disconnection chamber contain dielectrically insulating fluids. The interruption chamber is sealed with respect to a remaining part of the interruption pole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an interruption and disconnectingdevice for high- and/or medium-voltage applications, which containsdielectric insulation means and has a particular structure, so as toallow the reduction of the environmental impact of said insulationmeans.

2. Description of the Related Art

It is known that the interruption and disconnecting devices of the artgenerally comprise at least one interruption chamber and a disconnectionchamber which are connected to insulating bushings. These elements arearranged inside a structure which is sealed with respect to thesurrounding environment and is filled with a fluid insulating medium.With reference to FIG. 1, a block diagram is presented which illustratesan example of a typical structure of a known interruption anddisconnecting device used in a high-voltage substation.

A conductor of a main power line, indicated by the arrow 2, is connectedto a main distribution bar 3 by means of the interruption anddisconnecting device 1. Said interruption and disconnecting device 1comprises an insulating bushing 4 for connection to the line 2. adisconnection chamber 5, an interruption chamber 6, electric currentmeasuring devices 7 and 8 arranged at the ends of the interruptionchamber 6, and an insulating bushing 9 for connection to the bar 3 bymeans of a conductor 10. There are also two devices 11 and 12 used toearth the system.

The disconnection chamber 5 can be arranged both upstream and downstreamof the interruption chamber 6.

The device 1 is completely filled with an insulating medium in order toprevent electrical discharges between the various parts that are at highpotential differences.

A known embodiment of an interruption and disconnecting device accordingto the block diagram of FIG. 1 is presented with reference to FIG. 2.The insulating bushings 4 and 9 are arranged respectively in input andin output with respect to the interruption and disconnecting device 1.The insulating bushing 4 contains the conductor 2 of the main powerline, while the insulating bushing 9 contains the conductor 10 connectedto the main distribution bar (not shown in FIG. 2).

The insulating bushing 4 is connected to the disconnection chamber 5 bymeans of a coupling 13. The disconnection chamber 5 contains a fixedcontact 14 and a moving contact 15 for performing disconnection. Anearthing device 11 is also connected to the chamber 5 and connects, ifrequired, the main conductor 2 to the outer casing, 16 of the device 1,which is at ground potential by means of the supports 17, 18 and 19.Actuation elements 20 for moving the moving contact 15 are also placedinside the disconnection chamber 5. The disconnection chamber 5 isfurthermore separated from the insulating bushing 4 and from thedisconnection chamber 6 by means of the insulating partitions 21 and 22.

The interruption chamber 6 contains a moving contact 23 and a fixedcontact 24. The moving contact 23 is actuated by movement elements 25.Further, the earthing device 12 is connected to the interruption chamber6 and places the conductor 26 in output from the disconnection chamberat ground potential. The moving contact 23 is connected to the conductor10 in output from the interruption and disconnecting device 1. Theinterruption chamber 6 is separated from the insulating bushing 9 bymeans of the insulating partition 28. The insulating bushings 4 and 9,the interruption chamber 6 and the disconnection chamber 5 arecompletely filled with an insulating fluid, generally sulfurhexafluoride (SF₆), having a pressure which is higher than theatmospheric one. In order to maintain said internal pressure, requiredin order to achieve reduced insulation distances and therefore reducethe dimensions of the structure. the device 1 is completely sealed withrespect to the outside environment.

Alternative configurations with respect to the one described in FIGS. 1and 2 are possible. In particular, it is possible to use multipledisconnection chambers and multiple insulating bushings if it isnecessary to connect multiple distribution bars to the main power line.

In the interruption and disconnecting devices of the art, the insulationfluid that is generally used is sulfur hexafluoride (SF₆). Other knownfluids are fluorocarbons (FC), perfluorocarbons (PFC),perfluoropolyethers (PFPE) or mixtures thereof.

The use of these insulation means, particularly SF₆, which has thehighest dielectric insulation capacity, allows to considerably reducethe insulation distances and therefore to considerably reduce thedimensions of each single device, and therefore of the substation inwhich it is used, with respect to the use of insulating means, such asmineral oils. This fact leads to a considerable reduction ininstallation and operating costs.

It is known from the technical literature that known fluoridized gaseousinsulating means, in particular SF₆, may cause problems in terms ofenvironmental impact; furthermore they are considerably expensive.

Reducing the content of these insulating means by using alternativedielectric fluids, such as for example mixtures of SF₆ and nitrogen(N₂), pure nitrogen or noble gases leads to an increase in the requiredinsulation distances, since said alternative fluids have, for an equalpressure, a much lower dielectric strength and arch quenching powerthan, for example, SF₆ used in its pure state. Simple replacement of SF₆with other alternative insulation fluids without performing anystructural modification to the interruption and disconnecting devicewould cause malfunctions.

On the other hand, if the pressure of said alternative insulating fluidsis increased so as to ensure satisfactory dielectric strength and arcquenching power, it is necessary to resort to complicated structureswhich are economically scarcely competitive and scarcely reliable.

BRIEF SUMMARY OF THE INVENTION

The aim of the present invention is to provide an interruption anddisconnecting device for high- and/or medium-voltage applications, whosestructure has a reduced complexity and is capable of optimizing the useof the insulation means used, so as to considerably reduce theirenvironmental impact.

Within the scope of this aim, an object of the present invention is toprovide an interruption and disconnecting device for high- and/ormedium-voltage applications. which has a modular structure which allowsto partition the volume of the insulating fluids used inside theinterruption pole.

Another object of the present invention is to provide an interruptionand disconnecting device for high- and/or medium-voltage applications,in which it is possible to use different insulation means inside theinterruption pole.

Another object of the present invention is to provide an interruptionand disconnecting device for high- and/or medium-voltage applications,which allows easy maintenance and/or replacement of the electricactuation elements, particularly of the parts that are most exposed towear, such as the fixed contact and the moving contact of theinterruption chamber.

Another. but not last, object of the present invention is to provide aninterruption and disconnecting device for high- and/or medium-voltageapplications. which is highly reliable and relatively easy tomanufacture and at competitive costs.

This aim. these and other objects, which will become more apparenthereinafter, are achieved by an interruption and disconnecting devicefor high- and/or medium-voltage applications, comprising a disconnectionchamber and an interruption pole having a free volume accommodating aninterruption chamber which contains a moving contact and a fixedcontact, said interruption pole and said disconnection chambercontaining dielectrically insulating fluids. The device according to theinvention is characterized in that said interruption chamber is sealed.

In this way. the device according to the invention has a modularstructure which allows to optimize the use of dielectric fluids and toreduce the environmental impact; in fact, the dielectric fluids whichhave a high environmental impact are used only in the sealedinterruption chamber where a high arc quenching power is required.

Another advantage of the device according to the invention, consists inthe fact that the interruption chamber can be extracted from the mainbody of the electric interruption pole. This allows easy maintenanceand/or replacement of the parts most subject to wear during theinterruption and disconnection actuations by virtue of the possibilityto extract the sealed interruption chamber from the body of the electricpole. Furthermore, the device according to the invention is constitutedby a relatively small number of parts and ensures high reliability andeasy execution.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will become moreapparent from the description of some preferred but not exclusiveembodiments of an interruption and disconnecting device according to theinvention, illustrated by way of non-limitative example in theaccompanying drawings, wherein:

FIG. 1 is a block diagram of an example of a known interruption and.disconnecting device for high-voltage applications:

FIG. 2 is a schematic example of embodiment of an interruption anddisconnecting device for high-voltage applications;

FIG. 3 is a preferred but not exclusive embodiment of an interruptionand disconnecting, device according to the present invention; and

FIG. 4 illustrates schematically an alternative embodiment of aninterruption and disconnecting device according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in FIG. 3. the interruption and disconnecting deviceaccording to the invention comprises an input insulating bushing 51which is electrically connected to a main power line 50. A transformer53 is generally placed at the base of the insulating bushing 51 in orderto measure the current in input to the device. The insulating bushing 51is connected to an intermediate chamber 55 and is insulated from it bymeans of the partition 56.

The intermediate chamber 55 and the insulating bushing 51 are filledwith a dielectric fluid having a very low environmental impact or evennon-impact at all. for example a gaseous mixture of sulfur exafluorideand nitrogen (SF₆+N₂), or pure nitrogen gas (N₂), or air.

The intermediate chamber 55 is connected to an interruption pole 54 andis insulated from it by means of the partition 57; in its turn, theinterruption pole 54 is structurally connected to a disconnectionchamber 67 by means of the partition 73. The interruption pole 54 has afree volume, delimited by its casing 200 and the partitions 73 and 57,which accomodates an interruption chamber 63.

Said interruption chamber 63 contains interruption mechanisms whichcomprise at least a fixed contact 64 and at least a moving contact 59.The moving contact 59 is rigidly coupled to a guiding rod 61 which ismoved by an actuation system 62. for example of the linking rod-cranktype; the fixed contact 64 is connected to the disconnection chamber 67by means of a sealed connection 66.

As illustrated. the actuation system 62, the guiding rod 61 of themoving contact. the moving contact 59 and the fixed contact 64 arearranged inside the casino, of the interruption chamber 63; said casingof the chamber 63 can be made of insulating material, for examplefiberglass-reinforced plastic. at least in the part that surrounds themoving contact 59, the fixed contact 64 and the rod 62. Field shields 68and 69 are positioned around the casing of the interruption chamber 63;alternatively, the casing of the interruption chamber 63 can be used inits end part as field shield, without having to use the field shield 69and the closure flange 72.

The interruption chamber 63 is hermetically closed, in one end portion,by a flange 72 and is connected, at the opposite end, to the casing ofthe interruption pole 54 by means of the sealing flange 65; the casing,of the interruption pole 54 i can be made, for example. of conductingplastic.

In this way. the interruption chamber 63 is advantageously sealed withrespect to the remaining parts of the interruption pole 54. As aconsequence, the interruption chamber 63 can be filled with a highlydielectric fluoridized fluid, preferably sulfur exafluoride (SF₆), bymeans of the valve 71, while the interruption pole 54 is filled by meansof the valve 74, in the part of the free volume that is not occupied bythe chamber 63, with a different dielectric fluid, such as for example agaseous mixture of sulfur exafluoride and nitrogen (SF₆+N₂), or purenitrogen gas (N₂), or air. Alternatively, the interruption chamber 63can be filled with a dielectric fluoridized fluid chosen among the groupconstituted by perfluoropolyethers (PFPE), or perfluorocarbons (PFC), orfluorocarbons (FC).

This solution is particularly advantageous in that it allows tosegregate the. insulation means which have a high arc quenching power,but a high environmental impact as well, only where it is strictlynecessary, that is to say, inside the casing of the interruption chamber63 at the moving contact and at the fixed contact. In this manner thevolume of potentially polluting means used in the device is minimized.

Furthermore, their segregation inside the sealed chamber 63 allowsadequate control and prevents their dispersion into the atmosphere. Infact, the intermediate chamber 55 comprises a first portion of apiston-operated protection system 58 which interrupts the electricalconnection to the main power line if a pressure loss of the dielectricfluid used in the interruption pole 54 occurs. A second portion of thepiston-operated protection system 58 is positioned inside theinterruption pole 54 and is connected to the moving contact 59 of theinterruption chamber 63 by means of a sealed connection 60. According toan alternative embodiment, the conductor 50 of the insulating bushing 51can be directly connected to the interruption chamber 63.

A further advantage resides in the fact that, by acting on theconnections 60 and 66 and on the flange 65, the interruption chamber 63can be extracted from the interruption pole 54 by acting in thedirection of the arrow 70.

This solution is advantageous in that it allows to fully replace thechamber 63 if the parts subjected to the most intense wear, that is tosay, the moving contact 59 and the fixed contact 64, are damaged.considerably facilitating maintenance of the device.

The disconnection chamber 67 contains a moving contact 75 which, bymeans of a movement system 76, for example of the rack type, can beconnected to a first fixed contact 77 or to a second fixed contact 78.The first fixed contact 77 connects the moving contact 75 to the outputinsulating bushing 80, while the second fixed contact 78 connects themoving contact 75 to the outer casing 79, of the disconnector chamber67, which is at ground potential. The actuation system 76 is actuated byan actuator 81, for example an electric motor. The insulating bushing 80is separated from the disconnection chamber 67 by means of a partition82; a transformer 83 is generally placed at the base of the throughconductor 80 and measures the current in output from the device.

The disconnection chamber 67 and the insulating bushing 80 are filledwith a dielectric fluid having a very low environmental impact, or evennon-impact at all, such as for example a gaseous mixture of sulfurexafluoride and nitrogen (SF₆+N₂), or pure nitrogen gas (N₂), or air.

The interruption and disconnecting device according to the invention isparticularly suitable for use in high- and/or medium-voltage substationsfor distributing and transmitting electric power. Accordingly, thepresent invention also relates to a high- and/or medium-voltagesubstation for distributing and transmitting electric power,characterised in that it comprises an interruption and disconnectingdevice according to the invention.

With reference to FIG. 4, an alternative embodiment of the deviceaccording to the invention is schematically illustrated by indicatingonly the path of the current. In particular, the embodiment of FIG. 4foresees the use of an interruption pole 89, a sealed interruptionchamber 90 and three insulating bushings 91, 92 and 93.

The interruption chamber 90 is preferably filled with sulfur exafluorideSF₆, while the remaining volume of the interruption and disconnectingdevice is filled with insulating means having a very low environmentalimpact, or even non-impact at all, such as for example a mixture ofsulfur exafluoride and nitrogen (SF₆+N₂), or pure nitrogen gas (N₂), orair. As regards the constructive details, reference can be made forexample to FIG. 3. This embodiment is advantageous in that it allows toconnect the device to multiple secondary. distribution bars for examplein a substation.

In practices it has been found that the device according to theinvention fully achieves the intended aim, since, thanks to themodularity of its structure, it is possible to minimize the pollutionpotential of the interruption and disconnecting device by segregatingthe insulating means which have a high environmental impact only at theparts that require a higher arc quenching power.

The device thus conceived is susceptible of modifications andvariations, all of which are within the scope of the inventive concept;for example, it is possible to use multiple interruption chambers. Inany case, however, the advantages encountered in the above describedembodiments of the invention are maintained.

All the details may furthermore be replaced with technically equivalentelements. In practice, the considered circuit configurations, so long asthey are compatible with the specific use, as well as the singlecomponents, may be any according to requirements and the state of theart.

What is claimed is:
 1. An interruption and disconnecting device forhigh- and/or medium-voltage applications, comprising: a disconnectionchamber and an interruption pole having a casing which delimits a freevolume accommodating an interruption chamber which contains a movingcontact and a fixed contact, said interruption pole and saiddisconnection chamber containing dielectrically insulating fluids,characterized in that said interruption chamber is sealed with respectto a remaining part of the interruption pole.
 2. An interruption anddisconnecting device according to claim 1, wherein said sealedinterruption chamber and the free volume of the interruption pole thatis not occupied by the interruption chamber contain a first dielectricfluid and a second dielectric fluid, respectively, said first and seconddielectric fluids being different to each other.
 3. An interruption anddisconnecting device according to claim 2, wherein said first dielectricfluid comprises a dielectric fluoridized fluid.
 4. An interruption anddisconnecting device according to claim 3, wherein said dielectricfluoridized fluid is sulfur hexafluoride.
 5. An interruption anddisconnecting device according to claim 3, wherein said dielectricfluoridized fluid is chosen among the group constituted byperfluorocarbons, or fluorocarbons or perfluoropolyethers.
 6. Aninterruption and disconnecting device according to claim 2, wherein saidsecond dielectric fluid comprises a mixture of sulfur hexafluoride andnitrogen.
 7. An interruption and disconnecting device according to claim2, wherein said second dielectric fluid comprises pure nitrogen gas. 8.An interruption and disconnecting device according to claim 2, whereinsaid second dielectric fluid comprises air.
 9. An interruption anddisconnecting device according to claim 1, wherein the casing of theinterruption chamber also acts as an electric field shield.
 10. Aninterruption and disconnecting device according to claim 1, wherein thecasing of said interruption chamber is at least partly made of aninsulating material.
 11. An interruption and disconnecting deviceaccording to claim 1, wherein said sealed interruption chamber can beextracted with respect to the body of the interruption pole.
 12. A high-and/or medium-voltage substation for distributing and transmittingelectric power, comprising an interruption and disconnecting deviceaccording to claim
 1. 13. An interruption and disconnecting device forhigh- and/or medium-voltage applications, comprising: a disconnectionchamber and an interruption pole having a free volume accommodating aninterruption chamber which contains a moving contact and a fixedcontact, said interruption pole and said disconnection chambercontaining dielectrically insulating fluids, wherein said interruptionchamber is sealed, and said sealed interruption chamber can be extractedwith respect to a body of the interruption pole.